In conventional tree networks for testing points of a switching network, separate controls must be provided for each function which is to be performed. For example, U.S. Pat. No. 3,872,324 issued Mar. 18, 1975, a system for sequentially testing binary matrix points or contacts is shown. An address counter and decoder is provided with selection gating circuits directed toward relay contacts of an electromechanical switching matrix.
Other known circuits use many variations and combinations of latches and/or NOR circuits to provide the testing of various crosspoint or matrix contacts. Other systems provide a parallel matrix or map to control the testing of switching matrix crosspoints.